A known method of producing molten iron from iron ore is described generally as the HIsmelt Process and is based on forming a bath of molten iron and slag in a smelt reduction vessel which comprises:
i. bottom tuyeres for injecting solid carbonaceous material and a carrier gas into the molten bath; PA1 ii. top tuyeres for injecting iron ore, which may be pre-heated and/or partially reduced iron ore, into the molten bath from above the surface of the molten bath; and PA1 iii. top tuyeres for injecting air into the space above the surface of the molten bath to after-burn or post-combust reaction gases, such as CO and H.sub.2, released from the molten bath. PA1 "The invention is also based on the finding that the reactions in metallurgical reaction vessels are increased if fractions of the smelt are ejected from the bath like a fountain through the amount of gas introduced via the under-bath tuyeres and these fractions of the smelt move within the gas space in the form of drops, splashes and large particles of the smelt on ballistic trajectories that are only stopped when the smelt fractions hit the vessel wall or the smelt itself, collide with other smelt fractions or are drawn in by the oxidising gases blown onto the bath in the form of free jets." PA1 i. injecting a carrier gas and solid carbonaceous material and/or metal oxides and/or other solid material into the molten bath through a section of a side of the vessel that is in contact with the molten bath and/or from above the molten bath so that the carrier gas and solid carbonaceous material and/or metal oxides and/or other solid material cause molten metal to be projected into a space above the surface of the molten bath to form a transition zone; and PA1 ii. injecting an oxygen-containing gas into the space above the molten bath surface to afterburn reaction gases released from the molten bath into the transition zone. PA1 i. a metallurgical vessel for containing a molten bath, the vessel having a base, a side wall, a roof, and a gas outlet; PA1 ii. a first tuyere for injecting an oxygen-containing gas into a space in the vessel above the molten bath; and PA1 iii. a second tuyere above the molten bath or in a section of the side of the vessel that is in contact with the molten bath for injecting a carrier gas and solid carbonaceous material and/or metal oxides and/or other solid material into the molten bath to cause molten metal to be projected into a space above the surface of the molten bath to form a transition zone.
In accordance with the HIsmelt Process, the carbonaceous material acts as a reductant and an energy source.
An important feature of the HIsmelt Process is to form a transition zone in the gas space above the molten bath surface in which there are ascending and thereafter descending droplets or splashes of molten metal and slag which mix with reaction gases from the molten bath, top blown hot air, and the reaction gases from afterburning. The purpose of the transition zone is to facilitate the transfer to the molten bath of heat that is released by afterburning reaction gases from the molten bath. In accordance with the HIsmelt Process, the transition zone is formed by vigorous bottom injection of carbonaceous material and carrier gas into the molten bath which causes droplets and splashes of molten metal and slag to be projected from the molten bath.
A recent development of the HIsmelt Process is described in Australian patent application 48938/93 entitled "A Method for Intensifying the Reactions in Metallurgical Reaction Vessels" in the name of Technological Resources Pty Limited. The Australian patent application claims a priority date of Oct. 16, 1992 from German patent application 4234974.
The Australian patent application describes that an improvement in heat transfer efficiency of the HIsmelt Process can be obtained by controlling the bottom injection of carbonaceous material and carrier gas so that the transition zone is defined by a "fountain" of splashes and droplets of molten iron and slag. The paragraph bridging pages 5 and 6 of the patent specification of the Australian patent application describes that:
An object of the present invention is to provide an alternative method of generating a fountain-like transition zone.